Anti-neosporal IgG and IgE antibodies in canine neosporosis.

Neospora caninum infection provokes neurological disorders, recurrent abortion and death in dogs and cattle. Dogs are both intermediate and definitive host of N. caninum. Thus, the development of sensitive and specific immunoassays to diagnose canine neosporosis is essential to control this disease. This work investigated serum anti-neosporal IgG and IgE antibodies in 140 dogs represented by 30 healthy animals (group I), 11 dogs showing acute N. caninum infection (group II), 50 urban dogs with serological evidence of canine neosporosis in indirect fluorescent antibody test (IFAT) (group III) and 49 urban dogs without clinical and laboratory evidences of neosporosis (group IV). Enzyme-linked immunosorbent assay (ELISA) and western immunoblotting, both using a soluble N. caninum tachyzoite antigen (SNA), investigated these two isotypes of antibodies, while a Urea-ELISA measured the avidity of the IgG antibodies. Anti-Toxoplasma gondii IgG antibodies were also investigated in the animals. Anti-neosporal IgG was found in all animals from groups II and III, whereas 32.7% (16/49) of dogs from group IV were reactive. IgG antibodies of low avidity were demonstrated in dogs from group II (median 35.3%), while animals from groups III and IV had IgG antibodies of high avidity (medians of 61.5% and 61.7% respectively). IgE antibodies were found in four (13.3%) and five (16.6%) dogs from groups III and IV respectively. Dogs presenting acute infection (group II) or chronic infection (group III) had IgG antibodies to several neosporal antigens, mainly of 29-30 and 35 kDa, while 13 of 16 dogs from group IV recognized antigens from 14 to 170 kDa. Antibodies to T. gondii were detected in 36 of 50 (72%) sera from group III and 25 of 49 (51%) sera from group IV. We concluded that IgG-ELISA and Urea-ELISA with SNA may substitute for IFAT in both laboratory routine and epidemiological studies of canine neosporosis.